GRANTSBURG, Wis. (AP) -- Hundreds have joined the search for an autistic man missing since Sunday night after wandering away from a camp in the Grantsburg area of Burnett County.

25-year-old Keith Kennedy from Shoreview, Minn., vanished from the Trade Lake Camp, which is for developmentally disabled adults. His mother Linda Kennedy is among those who have searched through the woods.

Those leading the search say Kennedy speaks just four words and won't respond to a call. He also relies on anti-rejection drugs because of a kidney transplant and hasn't had the medication since disappearing, so his kidneys could start to shut down.

Nearly 300 volunteers searched Wednesday, including a team on horseback and crews in boats on a nearby river.

The search ended at dark and resumes Thursday at 7 a.m.

Kennedy is described as 5'6" tall, 140 pounds, and has an athletic build. He was last seen wearing an orange t-shirt and blue jeans. Anyone with information is asked to contact the Burnett County Sheriff's Department at (715) 349-2128.